When a silver halide light-sensitive material is processed with a developing solution which contains a compound capable of dissolving silver halides, e.g., thiosulfates and sulfites, elution of a good deal of silver complexes from the silver halide light-sensitive material into the developing solution takes place. The silver complexes eluted into the developing solution are reduced with the developing agent and converted to fine metallic silver, resulting in the generation of silver sludge in the developing solution.
A developing solution which contains sulfite in a high concentration, especially in a concentration of about 0.1 mol/liter or more, has excellent quality in maintaining its developing activity upon storage. However, having once been used, the developing solution tends to be contaminated and to cause developing-stain on surfaces of light-sensitive materials developed. This phenomenon turns out to be a serious disadvantage, especially when high temperature development is carried out using an automatic developing processor. This is because when development-processing is carried out using an automatic developing processor not only is silver sludge suspended in the developing solution but also silver particles adhere to walls of the processing tank and to rollers of the developing processor, and so the light-sensitive materials are subject to contamination with silver deposited thereon in the form of roller streaks, the so-called "silver stain", which silver appears yellow or brown by reflecting light therefrom. Silver stain is generated on the surface of a light-sensitive material equally, regardless of the quantity of light to which the light-sensitive material is exposed, and forms a colored layer on the surface resulting in a marked deterioration of the image quality obtained. Thus, silver stain directly spoils the quality of the photographic image. Therefore, when photographic light-sensitive materials are processed with such a developing solution as described above using an automatic developing processor, the qualities of the finished photographs tend to be spoiled to a great extent.
As an inhibitor of silver sludge or liquid contamination, 2-mercapto-1,3,4-thiadiazoles (as described in British Patent 940,169), 2-mercapto-1,3,4-oxadiazoles or 1-phenyl-5-mercaptotetrazole (as described in U.S. Pat. No. 3,173,789), D,L-6,8-dithiooctanoic acid (as described in U.S. Pat. No. 3,318,701), o-mercaptobenzoic acid (as described in British Pat. No. 1,144,481), aliphatic mercaptocarboxylic acids (as described in U.S. Pat. No. 3,628,955), L-thiazolidine-4-carboxylic acid (as described in J. Photogr. Sci., Vol. 13, page 233 (1965)), disulfide compounds [as described in Japanese Patent Application (OPI) No. 36029/77 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application")], 2-benzoxazolethiol and 2-benzimidazolethiol (as described in Photogr. Sci. Eng., Vol. 20, page 220 (1976)), and so on are known.
However, none of the above-described compounds, in a photographic developing solution which is capable of dissolving silver halide, especially in a developing solution containing sulfite in a high concentration, functions as a sludge inhibitor effectively enough to be completely satisfactory. For instance, aliphatic mercaptocarboxylic acid compounds are air oxidized, and consequently they tend to be oxidized by exposure to air and rapidly lose their sludge preventing effects; in addition, some of these compounds have unpleasant odors. The use of 1-phenyl-5-mercaptotetrazole or 2-benzoxazolethiol in a large amount can reduce liquid contamination in some cases; however, in other cases, these compounds react with silver ion to produce slightly soluble silver salts in the developing solutions, and thereby films are otherwise stained, rather than prevented silver stain. In addition, a large amount of such a compound in a developing solution disturbs the ability to achieve satisfactory photographic characteristics, since such compounds tend to inhibit development.
On the other hand, high temperature development, especially high temperature rapid processing using an automatic developing processor, is known as a process for carrying out development efficiently, and has proved fruitful upon the application to the processings of various kinds of light-sensitive materials. However, since light-sensitive materials are processed at high temperatures in this process, emulsion films subject to such processing must be prevented from becoming brittle at high temperatures so as to have sufficient mechanical strength to withstand the stress applied thereto by rollers and belts of the automatic developing processor. Therefore, it is necessary to devise a technique to increase the mechanical strength of an emulsion film as the development in a developing solution progresses and further, may be kept the mechanical strength during the processing.
For this purpose, the processing is carried out using a developing solution to which an aldehyde series hardener is added. According to this process, the total processing time can be shortened due to the processing at a high temperature, and the object of speeding up the processing can be attained. However, the development-processing with, e.g., developing solutions containing aldehydes, especially aliphatic dialdehydes, is attended by a significant generation of fog. The higher that the temperature of the developing solution is, and the longer the period of using the developing solution, the more significant is the tendency for the developing solution to cause fog. The occurrence of such fog resulting from aldehydes can be prevented by the use of a powerful fog restrainer, such as benzotriazole or 1-phenyl-5-mercaptotetrazole (which are described in L. F. A. Mason, Photographic Processing Chemistry, page 40, The Focal Press, 1966). However, the addition of such powerful fog restrainers to a developing solution retards the development to a great extent, and thereby the sensitivities of emulsions are reduced sharply.
5-Nitroindazole described in British Pat. No. 1,269,268 acts as an effective antifoggant in a developing solution containing an aldehyde series hardener. However, it has the disadvantages that an appropriate solvent is required because of its poor solubility in a developing solution, and its stability in a developing solution over a long period of time is low. Furthermore, satisfactory effect as a silver halide sludge inhibitor also is not exhibited.